1. Field of the Invention
The invention relates to thermoplastic compositions comprising a compatibilized polyphenylene ether-polyamide resin blend which is suitable for extrusion.
The invention also relates to articles formed out of the compositions of the invention.
2. Brief Description of the Related Art
Commercially available blends of polyphenylene ether and polyamide are less suitable for molding into the desired shapes by extrusion; they are manufactured by a compounding-extrusion step, followed by pellitization. The obtained pellets are then usually processed by injection molding into the desired shapes.
It is generally known to increase the molecular weight and hence the viscosity of thermoplastic resins to make them better suitable for molding by extrusion. The use of thermoplastics resins with increased viscosity results in higher melt strenght values as necessary for extrusion-molding.
The commercially most interesting blends of polyphenylene ether and polyamide comprise a continuous phase of polyamide in which the polyphenylene ether is dispersed. It would thus be expected that an increase of the viscosity of the polyamide only would make the blend more suitable for molding by extrusion. An increase of the melt viscosity did indeed occur by using a polyamide with increased viscosity in combination with a polyphenylene ether of standard viscosity. Unfortunately this blend with a normal polyphenylene ether showed a very undesirable effect: upon extrusion in the manufacturing step so-called die-swell occurred to such an extent that the product was not uniform in thickness and not well processable.